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Structurally rigid copolyester thermoplastics were synthesized from 1,4‐cyclohexanedimethanol and the diesters dimethyl biphenyl‐4,4′‐dicarboxylate and dimethyl 2,6‐naphthalenedicarboxylate (DMN) via conventional melt transesterification. Conventional differential scanning calorimetry (CDSC) showed all compositions to exhibit multiple endotherms upon heating. Wide‐angle X‐ray diffraction analysis showed copolyester compositions to exhibit the crystalline structure of either the homopolyester Poly(1,4‐cyclohexylenedimethylene 2,6‐naphthalate) (PCN) or the homopolyester Poly(1,4‐cyclohexylenedimethylene 4,4′‐bibenzoate) (PCB), but not both simultaneously. Further thermal analysis using CDSC and fast DSC investigated the origin of the multiple endotherm behavior. While three endotherms are observed for low heating rates, the upper two endotherms appear to merge at heating rates about 1–5 °C s−1 and a single endotherm remains above heating rates about 10–50 °C s−1. While the behavior of the upper two endotherms is undeniably consistent with the mechanism of melting–recrystallization–remelting (MRR), we suggest that the low endotherm is likely associated with the melting of constrained secondary crystals, although MRR effects cannot be ruled out. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 973–980 [ABSTRACT FROM AUTHOR]

The ability of a multiphase copolymer to exhibit both the physical properties of liquid crystalline and elastomeric polymers enables a variety of emerging applications. Traditional synthetic methods often require many steps to achieve such diversity in a copolymer. This work describes the synthesis and characterization of biphenyl-containing segmented copolyesters in a single step. A fundamental investigation of the thermal and thermomechanical properties as a function of methylene spacer length demonstrates a relationship between melting temperature and even/odd spacer lengths. DSC and SAXS analysis reveal microphase separation in these randomly segmented copolyesters. The copolymers retain a liquid crystalline morphology despite the incorporation of a flexible oligomeric polyether, and melting and isotropic temperatures ranged from 77 to 167 °C and 117 to 217 °C, respectively. Wide angle X-ray diffraction provides further insight into the effect of the soft segment on the highly crystalline nature of the segmented copolyesters. Thermomechanical analysis and tensile testing elucidate the effect of hard segment (HS) content and structure. Plateau moduli range from ≈5 to 150 MPa and increasing from 50 to 75 wt% HS doubled tensile strain. This synergy will enable superior fabrication and processing of intricate electronic devices that require high-thermal properties and mechanical durability. [ABSTRACT FROM AUTHOR]

Embedded fiber retraction was used to investigate the interfacial tension and fiber lifetime of an immiscible polyester/polyamide system, with and without ionic functionality incorporated onto the polyester as compatibilizing groups. The ionic groups reduce the interfacial tension of the system from 7.55 dyne/cm to 1.49 dyne/cm when incorporated at 5.5 mole% into the polyester. In addition, fiber lifetime increased by a factor of 4–5 with the incorporation of ionic functionality. These results correlate extremely well with previously published observations of the ionomer‐compatibilized blends and confirm the influence of interfacial tension on blend morphology. The initial aspect ratio of the fiber should be between three and 12 for consistent and reproducible results. [ABSTRACT FROM AUTHOR]

Examines the utilization of sulfonated polyester ionomers as minor-component compatibilizers in blends of an amorphous polyester and polyamide. Preparation of the blends using twin-screw extrusion; Blend morphology; Thermal and mechanical properties of the extruded blends.

Provides information on study which investigated the compatibility of polyester ionomers with polar polymers for their potential use as minor component compatibilizers. Experimental design; Results and discussion; Conclusions.

A new synthetic strategy using melt transesterification enabled selective control of ionic charge placement into the hard segment or soft segment block of segmented copolyesters. Dynamic mechanical analysis of sulfonated soft segment copolyesters revealed an increase in the low-T g transition and rubbery plateau storage modulus as a function of sulfonation level. Sulfonated hard segment copolyesters displayed similar rubbery plateau moduli and decreasing flow temperature from 145 to 90 °C. Dynamic melt rheology and in situ, variable temperature small-angle X-ray scattering determined the non-sulfonated copolyester order-disorder transition at 150 ± 5 °C, which was ∼60 °C above the hard segment T g . Atomic force microscopy revealed sulfonated hard segment copolyesters contained more disordered surface morphologies. Sulfonated soft segment copolyesters demonstrated increased tensile stress and improved tensile strain from 18 to 170% with increasing ion content. The enhanced mechanical performance of sulfonated soft segment was attributed to the preserved microphase-separated morphology and the presence of physical crosslinks from electrostatic interactions. [ABSTRACT FROM AUTHOR]

Abstract The substitution of a linear biphenyl monomer with its meta isomer in liquid crystalline polyesters affords (co)polyesters with tunable liquid crystalline (LC) and thermomechanical properties. Melt transesterification afforded two (co)polyester series based on the semi-aromatic homopolymers poly(diethylene glycol 4,4′ bibenzoate) and poly(butylene 4,4′ bibenzoate) at high molecular weights. In each series, the linear dimethyl-4,4′ bibenzoate (4,4'BB) was systematically exchanged with its kinked isomer, dimethyl-3,4′ bibenzoate (3,4'BB). The incorporation of the meta isomer resulted in tunable crystalline and LC properties. Differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS), X-ray diffraction (XRD), and polarized optical microscopy (POM) elucidated that the kinked structure of 3,4'BB disrupted crystallization at low incorporations, significantly lowering the melting transition temperature (>50 °C) in each series. The LC properties were less impacted due to the biphenyl structure resulting in LC glasses with wide mesogenic windows. Dynamic mechanical analysis (DMA) further demonstrated the tunable nature of the thermomechanical properties resulting from the (co)polymerization of these isomers. Graphical abstract Image 1 Highlights • Synthesized two liquid crystalline (co)polyesters utilizing isomeric comonomers. • Liquid crystalline order and thermal properties investigated upon increased incorporation of kinked monomer. • Liquid crystalline glass morphologies observed at high linear monomer compositions. [ABSTRACT FROM AUTHOR]

Multiblock copolymers of poly(arylene ether sulfones) (PAESs) and poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) were synthesized via melt-phase polymerization. PAES oligomers (M n = 2000 g/mol) were synthesized with hydroxyethoxyl end groups, and then reacted with dimethyl terephthalate (DMT) and 1,4-cyclohexanedimethanol (CHDM) to obtain segmented copolymers with the goal of introducing semi-crystallinity into the PAES segmented block copolymers. Two CHDMs ( all trans and cis/trans = 30/70) were used for comparison. Weight percentages of PCT segments varied from 20 wt% to 80 wt%. According to the results measured by DSC, DMA and WAXS, the copolymers crystallized when the content of PCT segment was above 50 wt%, and the crystallinity of the copolymers exhibited a proportional dependence on the weight percentage of PCT segments. Segmented copolymers with trans -CHDM as the polyester segment exhibited a higher level of crystallinity than the 30/70 CHDM mixture. [ABSTRACT FROM AUTHOR]